Professor Kitiro Tanaka developed the Relief Contour Method to emphasize topographic view on an orthographic map in the middle of the 20th century. The above method allows a cartographer to create contours with variation of line thickness representing brightness of ground surface caused by the incoming light from northern-westward in an altitude 45 degrees. Articles of the method include mathematical explanations for a cartographer to draw the contours producing a stereoscopic effect covering continuously over a map. The Relief Method was adopted to publish a bathymetric chart of adjacent seas of Japan in a scale of 1: 8,000,000 by Japan Hydrographic Department in 1952. The method is most suitable to describe topographic knowledge around Japan for people who have scientific interest in deep seas. Although it has not progressed to explain the mechanism of the vision of human eyes effected by the method, modified relief contour methods were coming up in the field of computer cartography since last quarter of the 20th century. If an improved visual recognition model for feeling of three-dimensionality were developed, more refined methods derive from the Tanaka's method would be applied to computer cartography.
